My '99 Ford Ranger shudders a bit at freeway speeds (60+ mph). Also slight pulsation & some rumbling at lower speeds. Tires & shocks about 17k miles old; rotation & balance about 6k mi ago; new ball joints & alignment about 1800 mi ago; front brakes renewed about 18k mi ago; no visible signs of unusual tire wear, separation or other tire issues. Could this possibly be a warped brake rotor or failing front wheel bearing? If that’s not feasible, any other ideas? I don’t want to just swap parts till the prob goes away.